/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;
using java = biz.ritter.javapi;
using org.apache.commons.collections;

namespace org.apache.commons.collections.iterators
{

    /**
     * An Iterator that restarts when it reaches the end.
     * <p>
     * The iterator will loop continuously around the provided elements, unless 
     * there are no elements in the collection to begin with, or all the elements
     * have been {@link #remove removed}.
     * <p>
     * Concurrent modifications are not directly supported, and for most collection
     * implementations will throw a ConcurrentModificationException. 
     *
     * @since Commons Collections 3.0
     * @version $Revision: 7135 $ $Date: 2011-06-04 20:58:43 +0200 (Sa, 04. Jun 2011) $
     *
     * @author <a href="mailto:joncrlsn@users.sf.net">Jonathan Carlson</a>
     * @author Stephen Colebourne
     */
    public class LoopingIterator : ResettableIterator
    {

        /** The collection to base the iterator on */
        private java.util.Collection<Object> collection;
        /** The current iterator */
        private java.util.Iterator<Object> iterator;

        /**
         * Constructor that wraps a collection.
         * <p>
         * There is no way to reset an Iterator instance without recreating it from
         * the original source, so the Collection must be passed in.
         * 
         * @param coll  the collection to wrap
         * @throws NullPointerException if the collection is null
         */
        public LoopingIterator(java.util.Collection<Object> coll)
        {
            if (coll == null)
            {
                throw new java.lang.NullPointerException("The collection must not be null");
            }
            collection = coll;
            reset();
        }

        /** 
         * Has the iterator any more elements.
         * <p>
         * Returns false only if the collection originally had zero elements, or
         * all the elements have been {@link #remove removed}.
         * 
         * @return <code>true</code> if there are more elements
         */
        public bool hasNext()
        {
            return (collection.size() > 0);
        }

        /**
         * Returns the next object in the collection.
         * <p>
         * If at the end of the collection, return the first element.
         * 
         * @throws NoSuchElementException if there are no elements
         *         at all.  Use {@link #hasNext} to avoid this error.
         */
        public Object next()
        {
            if (collection.size() == 0)
            {
                throw new java.util.NoSuchElementException("There are no elements for this iterator to loop on");
            }
            if (iterator.hasNext() == false)
            {
                reset();
            }
            return iterator.next();
        }

        /**
         * Removes the previously retrieved item from the underlying collection.
         * <p>
         * This feature is only supported if the underlying collection's 
         * {@link Collection#iterator iterator} method returns an implementation 
         * that supports it.
         * <p>
         * This method can only be called after at least one {@link #next} method call.
         * After a removal, the remove method may not be called again until another
         * next has been performed. If the {@link #reset} is called, then remove may
         * not be called until {@link #next} is called again.
         */
        public void remove()
        {
            iterator.remove();
        }

        /**
         * Resets the iterator back to the start of the collection.
         */
        public void reset()
        {
            iterator = collection.iterator();
        }

        /**
         * Gets the size of the collection underlying the iterator.
         * 
         * @return the current collection size
         */
        public int size()
        {
            return collection.size();
        }

    }
}